Arnold Schwarzenegger and his wife Maria Shriver before he admitted fathering a lovechild, and the couple split. Photograph: Jason Merritt/FilmMagic

Have relations between men and women reached a new low? Powerful men from Sir Fred Goodwin to Arnold Schwarzenegger – along with nameless footballers and actors still hanging on to their superinjunctions – are revealed to have risked marriage and career over an affair. Kenneth Clarke was forced to confirm last week that he does think all rape is serious.

According to one of the world's bestselling psychologists, the revelations of misconduct and ill-considered remarks indicate a disturbing deepening of the divide between the sexes.

Since its publication nearly two decades ago, Dr John Gray has sold 50 million copies of Men Are from Mars, Women Are from Venus, to people desperate to understand what was going wrong in their relationships and bedrooms and why. The book's title has become a virtual shorthand for describing a presumed gulf between the sexes. Gray's controversial view was that behavioural differences were hard-wired into our gender-specific brains.

Speaking to the Observer in the wake of the recent sequence of sex-related scandals, Gray claimed that the gulfs in understanding that divide men from women are being exacerbated by hormones, which are working against people achieving monogamy in a stressful world. "Why are the sexes not getting along? It's just that people have new needs and they don't know what to do about them; they want passion but don't know how to sustain it," he said.

His theory is that powerful men have higher than average levels of testosterone, which they seek to "top up" when their reserves become depleted. One way they do that is to have an affair. According to Gray, long-term relationships generate oxytocin, dubbed the "love hormone", which encourages bonding between couples and helps to lower female stress levels. But that benefit comes at a price for alpha male partners.

"With oxytocin and alpha men, as the women's stress level goes down when she gets oxytocin from a loving monogamous relationship, the man's testosterone level is going down, so he's getting more stressed and more inclined to seek out risky behaviour to push it back up again. The concept is that intimacy can lower a man's sexual drive."

He believes that is why men like Schwarzenegger are driven to risky affairs, and why women will no longer tolerate it. "Arnie loves his wife deeply, but he's breached trust and abused his power and men can't get away with that any more," said Gray, whose latest book is out in the US is called Venus on Fire, Mars on Ice.

"The fact that Kissinger was once voted the sexiest man in America suggests women have always have been attracted to alpha males. Power and influence has an effect on men that says, 'I'm entitled'. They've a greater sense of entitlement to breaking the rules, to corruption, but also they typically have higher levels of testosterone, which they depend on to function.

"Power and influence has long excused men behaving badly. But what I see is a trend which started in the US even before Bill Clinton, when Gary Hart was running for president in 1988 and they had pictures of him with a woman in a bathing suit who was not his wife, and he was kicked out. Suddenly it wasn't OK. Values became more important. That was a turning point, a shift in the consciousness of the public, a greater awareness of suppression of women's rights. And as more women were in the workplace, in newsrooms and in courtrooms they were outraged, unlike the way male reporters colluded to suppress the sexual proclivities of JFK."

In days gone by women would have turned a blind eye, says Gray. "When I was raised, in the fifties, for my mother a good husband was someone who had a job, he didn't drink or smoke too much, he didn't yell or shout. She said that for that generation a provider was what women wanted. She had a lifestyle which kept her oxytocin levels up so she was happy. She says the lack of romance wasn't a big deal and if she suspected he might have 'other responsibilities' somewhere else it didn't bother her. In the eighties women wanted romance. In the nineties women wanted communication. Now noughties women want romance, then communication, then they are saying, 'I get nothing in the way of domestic help.' That's all mixed up.

So while women are obsessing with help with the housework and men are obsessing with casual sex, their relationships are being riven apart.

"In America the startling statistic is that the average length of a relationship is five years. That's three years of passion and two years of gathering the evidence they need to leave."

Gray's theories are contested by scientists who insist society, not nature, shapes gender politics. The associate professor of neuroscience at the Chicago Medical School, Lise Eliot, said: "Yes, boys and girls, men and women, are different but most of those differences are far smaller than the Men Are from Mars stereotypes suggest."

Gray insists he is not saying men are enslaved by their hormones and that divides can and should be bridged. "Men are basically wired up to be polygamous but they are also wired up to be violent. We learn to sublimate these urges and to civilise the experience. If I see an attractive women, I use my brain to remember my wife, and my arousal goes back to my wife – you train yourself with that, you control your urges. That's why I've been married for 26 years."